HuntingNet.com Forums - scratchin my head on velocity

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ORIGINAL: bigcountry

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ORIGINAL: haugenna

I went to the range three times last week and shot over a chronograph. I shot the same load on Monday as I did on Friday and Saturday. All days were calm days, 60-70 degrees and I pushed a 200 Gr TSX 3292fps was avg, hi 3301, lo 3284, with 100 Gr. RL 25.

I went back Friday and Saturday and only achieved 3170 avg. One thing I did learn, is that most reloadingbooks are full of it when they talk about powders and velocity. What could have been the factor? Any advice. Primers, bullet, powder were all the same. Does trim length and bullet seating depth make that big of a difference? COL was 3.777 on Monday and Saturday and 3.770 on Friday. All shots were with warm, not hot but not cold, barrels. Does ten degrees temperature make that big of a difference? Any advice would be helpful.

I have same issues with my pact and chony F1. What I found was light conditions was the dominating factor. But it doesn't make sense.

I shot over a friends oehler and it was rock solid one day as it was a year before that. You get what you pay for in chronys.

I like you starting suspecting weather and all. But did the tape test. I put clear tape over my sensors to see what would happen. I lost velocity. By 100fps. Sometimes more.

So I started experiementing taking one peice off the front and so on.

I am a EE, so know little something about timers, and photocells. One thing I do know is temp has a big effect sometimes on circuits. But I am having a hard time wrapping my arms around this problem. Light is light, so theorectically, it shouldn't make a difference on timing no matter how cheap the components are for a F1 or Gamma, or whatever. So I conclude it has to be with the timer circuitry. Any of you guys who have went thru physics or Engineering program has probably has to build a crude timing source from a Quartz timer or something and know you can adjust timing by a few factors but not by much.

You may be correct theoretically, but too many users of the various Shooting Chronys have noted significantly different velocity readings from the same load when lighting conditions were different for the variations to be caused by some other factor. There are differences between sunny and cloudy days, as well as variations due to sun angle on sunny days.

I have also noted similar effects when using early models of the Oelhers with Skyscreens.......